Metal droplet additive manufacturing device

Abstract

The present invention provides a metal micro-droplet additive manufacturing device, which relates to the technical field of metal additive manufacturing and includes a heating mechanism, a feeding mechanism and an electromagnetic driving mechanism; by using molten liquid metal micro-droplets to remelt, solidify and stack layer by layer, using metal wire materials as printing consumables to replace the expensive metal powders required for traditional metal additive manufacturing, without integrating expensive laser, arc, electron beam equipment, nor post-treatment processes such as sintering, using a non-contact electromagnetic driving method, replacing the printing material with molten liquid metal substances, and utilizing the magnetohydrodynamic properties of liquid metals to generate metal micro-droplets with higher frequencies and droplet masses, and directly using them for 3D printing of metal parts, alleviating the technical problems of high raw material costs, expensive equipment, low printing rates in the prior art, resulting in high costs of metal 3D printing.

Description

Technical Field

[0001] The present invention relates to the technical field of metal additive manufacturing, and more particularly to a metal micro-droplet additive manufacturing device. Background Art

[0002] Metal additive manufacturing technology has been widely applied in the industrial field and is suitable for the processing and manufacturing of complex and customized parts. Common metal 3D printing methods include powder bed fusion, powder feeding, wire feeding, or binder jetting-based methods; these technologies require high-power lasers and inert environments or extensive post-processing, especially the binder jetting method, which requires pyrolysis after material ejection and before sintering.

[0003] Therefore, the metal required in the existing metal additive manufacturing is metal powder, which requires the integration of expensive laser, arc, and electron beam equipment, and also requires post-processing technologies such as sintering. As a result, the raw material cost, equipment cost, and printing rate of the existing metal additive manufacturing are high, resulting in the still high cost of metal 3D printing in the existing technology. Summary of the Invention

[0004] The purpose of the present invention is to provide a metal micro-droplet additive manufacturing device to alleviate the technical problems of high raw material cost, high equipment cost, low printing rate, and high cost of metal 3D printing existing in the prior art.

[0005] A metal micro-droplet additive manufacturing device provided by the present invention includes: a heating mechanism, a feeding mechanism, and an electromagnetic driving mechanism;

[0006] The electromagnetic driving mechanism includes an excitation inductance coil, a crucible, and a nozzle; the feeding mechanism is internally connected to the crucible, and the feeding mechanism is used to convey metal wire materials into the crucible. The heating mechanism is annularly arranged outside the crucible, and the heating mechanism is used to heat and melt the metal wire materials in the crucible to form a liquid metal molten pool;

[0007] The nozzle is connected to the crucible, and the excitation inductance coil is annularly arranged outside the nozzle. The excitation inductance coil is used to provide a Lorentz force into the nozzle under the action of energization to control the formation of metal micro-droplets spraying or droplet pinching-off and stopping of the liquid metal in the nozzle.

[0008] In a preferred embodiment of the present invention, a control body is further included;

[0009] The control body is respectively electrically connected to the feeding mechanism, the heating mechanism, and the electromagnetic driving mechanism. The control body can adjust the opening and closing of the feeding mechanism to control the height of the molten metal pool surface in the crucible. The control body can control the heating temperature of the heating mechanism, and the control body can control the voltage pulse width modulation waveform applied across the excitation inductance coil in the electromagnetic driving mechanism.

[0010] In a preferred embodiment of the present invention, it further includes a housing and a heat insulation layer;

[0011] The heating mechanism, the feeding mechanism, and the electromagnetic driving mechanism are all installed inside the housing. The housing has a sandwich layer, and the heat insulation layer is filled in the sandwich layer. The heat insulation layer is uniformly arranged along the circumferential direction of the housing.

[0012] In a preferred embodiment of the present invention, the housing includes an outer housing body, an upper end cover, an inner housing body, and a nozzle housing;

[0013] The outer housing body is provided with an accommodation space. The inner housing body is located inside the accommodation space and is in contact with the inner wall of the outer housing body. The upper end cover is hermetically connected to the end of the outer housing body and is connected to the inner housing body. The nozzle housing is sleeved outside the nozzle, and the inner housing body is in contact and fixed with the nozzle housing.

[0014] In a preferred embodiment of the present invention, the housing further includes a crucible fixing frame;

[0015] The crucible fixing frame is located between the inner housing body and the crucible. The crucible fixing frame clamps the outside of the crucible, and the crucible fixing frame is fixed to the inner housing body by step clamping.

[0016] In a preferred embodiment of the present invention, the feeding mechanism includes a metal wire material supply pipeline, a laser displacement sensor, and a quartz window;

[0017] An observation hole is opened on the upper end cover. The quartz window is hermetically connected to the observation hole, and a feeding channel is opened on the quartz window. The metal wire material supply pipeline extends into the accommodation space through the feeding channel and is communicated with the crucible. The metal wire material supply pipeline is communicated with an external metal wire material conveying mechanism;

[0018] The laser displacement sensor is arranged corresponding to the quartz window, and the laser displacement sensor is electrically connected to the control main body. The laser displacement sensor is used to detect the liquid level height information of the metal molten pool in the crucible and transmit this height information to the control main body, and the control main body correspondingly controls an external metal wire feeding mechanism to feed metal wire to the metal wire supply pipeline.

[0019] In a preferred embodiment of the present invention, the heating mechanism includes a heating coil electrode, a heating coil, a thermocouple connecting pipe, and a thermocouple;

[0020] The upper end cover is provided with an electrode hole and a thermocouple through hole. The heating coil is arranged annularly along the outside of the crucible. The heating coil electrode penetrates through the electrode hole and is electrically connected to the heating coil, and the heating coil electrode is hermetically connected to the electrode hole;

[0021] The thermocouple is attached to the outer side wall of the crucible. The thermocouple connecting pipe penetrates through the thermocouple through hole and is electrically connected to the thermocouple; the thermocouple is electrically connected to the control main body. The thermocouple is used to detect the temperature information of the crucible and transmit this temperature information to the control main body, and the control main body correspondingly controls the voltage and output power of the heating coil electrode.

[0022] In a preferred embodiment of the present invention, the thermocouple connecting pipe and the thermocouple through hole are sealed with ceramic glue.

[0023] In a preferred embodiment of the present invention, the upper end cover is provided with an inert gas channel, and the inert gas channel is communicated with the inside of the crucible.

[0024] In a preferred embodiment of the present invention, the electromagnetic driving mechanism further includes an excitation coil water cooling ring, a water cooling ring sealing cover, and a sealing ring;

[0025] The excitation coil water cooling ring is located at one end of the housing main body away from the upper end cover. The water cooling ring sealing cover is located between the excitation coil water cooling ring and the housing main body. The water cooling ring sealing cover is respectively connected to the excitation coil water cooling ring and the housing main body. The sealing ring is located between the excitation coil water cooling ring and the water cooling ring sealing cover. The excitation coil water cooling ring is sleeved outside the nozzle housing;

[0026] The excitation coil water cooling ring is provided with an annular channel, a water inlet, and a water outlet. The water inlet and the water outlet are respectively located on opposite sides of the annular channel. The excitation inductance coil is accommodated in the annular channel, and the annular channel is used for flowing coolant to adjust the temperature of the excitation inductance coil.

[0027] The metal micro-droplet additive manufacturing device provided by the present invention includes: a heating mechanism, a feeding mechanism, and an electromagnetic driving mechanism; the electromagnetic driving mechanism includes an exciting inductance coil, a crucible, and a nozzle; the feeding mechanism is internally connected to the crucible, and the feeding mechanism is used to convey metal wire materials into the crucible. The heating mechanism is arranged annularly outside the crucible, and the heating mechanism is used to heat and melt the metal wire materials in the crucible to form a molten metal pool; the nozzle is connected to the crucible, and the exciting inductance coil is arranged annularly outside the nozzle. The exciting inductance coil is used to provide a Lorentz force into the nozzle under the action of energization to control the molten metal in the nozzle to form metal micro-droplets for spraying or droplet pinching-off to stop; by using the molten liquid metal micro-droplets to remelt, solidify, and stack layer by layer to form a shape, using metal wire materials as printing consumables, replacing the expensive metal powders required for traditional metal additive manufacturing, without the need to integrate expensive laser, arc, and electron beam equipment, nor post-treatment processes such as sintering. Using a non-contact electromagnetic driving method, the printing material is replaced with a molten liquid metal substance. Using the magnetohydrodynamic properties of the liquid metal, metal micro-droplets with higher frequencies and droplet masses can be generated and directly used for 3D printing of metal parts, alleviating the technical problems of high raw material costs, expensive equipment, and low printing rates existing in the prior art, resulting in high costs for metal 3D printing. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a schematic diagram of the overall structure of the metal micro-droplet additive manufacturing device provided by the embodiment of the present invention;

[0030] Figure 2 [[ID=!3]]It is a schematic diagram of the cross-sectional structure of the metal micro-droplet additive manufacturing device provided by the embodiment of the present invention;

[0031] Figure 3 It is a schematic diagram of the magnetic field direction and the force on the metal inside the nozzle during the positive voltage pulse section of the metal micro-droplet additive manufacturing device provided by the embodiment of the present invention;

[0032] Figure 4 It is a schematic diagram of the magnetic field direction and the force on the metal inside the nozzle during the negative voltage pulse section of the metal micro-droplet additive manufacturing device provided by the embodiment of the present invention;

[0033] Figure 5 It is a schematic diagram of the top view structure of the electromagnetic driving mechanism of the metal micro-droplet additive manufacturing device provided by the embodiment of the present invention;

[0034] Figure 6 for Figure 5 AA cross-sectional structural diagram of a metal droplet additive manufacturing device provided in the embodiment;

[0035] Figure 7 A waveform diagram of the applied pulse voltage of the metal droplet additive manufacturing device provided by an embodiment of the present invention;

[0036] Figure 8 A waveform diagram of the applied pulse current of the metal droplet additive manufacturing device provided by an embodiment of the present invention;

[0037] Figure 9 A schematic diagram of charging the excitation inductor coil of the metal droplet additive manufacturing device provided by an embodiment of the present invention;

[0038] Figure 10 Schematic diagram of the discharge of the excitation inductor of the metal droplet additive manufacturing device provided in an embodiment of the present invention.

[0039] Icons: 100-electromagnetic drive mechanism; 101-excitation inductor coil; 102-crucible; 103-nozzle; 104-excitation coil water-cooling ring; 114-annular channel; 124-water inlet; 134-water outlet; 105-water-cooling ring sealing cover; 106-sealing ring; 200-feeding mechanism; 201-metal wire supply pipeline; 202-laser displacement sensor; 203-quartz window; 300-heating mechanism; 301-heating ring electrode; 302-heating ring; 303-thermocouple connecting tube; 304-thermocouple; 400-shell; 401-shell body; 411-insulation layer; 402-upper end cover; 412-inert gas channel; 403-inner shell body; 404-nozzle shell; 405-crucible fixing bracket; 500-metal molten pool liquid level. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] like Figures 1 - 10As shown in the figure, a metal micro-droplet additive manufacturing device provided in this embodiment includes a heating mechanism 300, a feeding mechanism 200, and an electromagnetic driving mechanism 100. The electromagnetic driving mechanism 100 includes an exciting inductance coil 101, a crucible 102, and a nozzle 103. The feeding mechanism 200 is internally connected to the crucible 102. The feeding mechanism 200 is used to convey metal wire materials into the crucible 102. The heating mechanism 300 is arranged annularly outside the crucible 102. The heating mechanism 300 is used to heat and melt the metal wire materials in the crucible 102 to form a molten metal pool. The nozzle 103 is connected to the crucible 102. The exciting inductance coil 101 is arranged annularly outside the nozzle 103. The exciting inductance coil 101 is used to provide a Lorentz force into the nozzle 103 under the action of energization to control the molten metal in the nozzle 103 to form metal micro-droplets for spraying or droplet pinching off and stopping.

[0042] It should be noted that the implementation principle and method of the metal micro-droplet additive manufacturing device provided in this embodiment are different from the metal additive manufacturing technology in the prior art. In this embodiment, by directly using molten liquid metal micro-droplets to remelt, solidify, and stack layer by layer, and using metal wire materials as printing consumables, it replaces the expensive metal powders required for traditional metal additive manufacturing, without the need to integrate expensive laser, arc, and electron beam equipment, nor post-treatment processes such as sintering. Specifically, based on electromagnetics and fluid mechanics, the high-temperature molten liquid metal is controllably sprayed from the nozzle 103 in the form of extremely small-sized spherical droplets at a high frequency. Combining with the displacement platform located below the nozzle 103, the metal material is stacked and solidified layer by layer, and finally the required metal parts are printed.

[0043] Specifically, liquid metal is a special incompressible fluid with the properties of high electrical conductivity, high density, high surface tension, and low viscosity of metals. It can quickly respond to changes in the spatial electromagnetic field. When the magnetic induction intensity vector field B in space changes, an instantaneous induced electromotive force and induced current will be generated in the liquid metal. The induced current and the magnetic field in space act together to generate a Lorentz force inside the liquid metal. By reasonably controlling the magnitude, direction, and action time of Lorentz, a pulsed pressure wave can be formed inside the molten liquid metal pool. This pulsed pressure wave can be transmitted downward along the vertical direction to the nozzle 103, squeezing the liquid metal at the nozzle 103 to overcome the surface tension and spray in the form of droplets, thereby realizing the on-demand spraying and printing of molten liquid metal micro-droplets. This embodiment has the advantages of high driving frequency, strong driving force, and non-contact driving. It is applicable to a variety of high-melting-point metals (such as: aluminum, stainless steel alloy, copper alloy, titanium alloy, etc.). According to the different melting points and electrical conductivities of different metals, the heating temperature and exciting current parameters of the device can be quantitatively changed during the actual operation process.

[0044] The metal micro-droplet additive manufacturing device provided in this embodiment includes: a heating mechanism 300, a feeding mechanism 200, and an electromagnetic driving mechanism 100; the electromagnetic driving mechanism 100 includes an exciting inductance coil 101, a crucible 102, and a nozzle 103; the feeding mechanism 200 is internally communicated with the crucible 102, and the feeding mechanism 200 is used to convey metal wire materials into the crucible 102. The heating mechanism 300 is annularly arranged outside the crucible 102, and the heating mechanism 300 is used to heat and melt the metal wire materials in the crucible 102 to form a molten metal pool; the nozzle 103 is connected to the crucible 102, and the exciting inductance coil 101 is annularly arranged outside the nozzle 103, and heat insulation materials are filled in its gap. The exciting inductance coil 101 is used to provide a Lorentz force into the nozzle 103 under the action of energization to control the molten metal in the nozzle 103 to form metal micro-droplets for spraying or droplet pinching-off and stopping; by using the melting, solidification, and stacking of molten liquid metal micro-droplets layer by layer, and using metal wire materials as printing consumables, it replaces the expensive metal powders required for traditional metal additive manufacturing, without the need to integrate expensive laser, arc, and electron beam equipment, nor post-treatment processes such as sintering. By using a non-contact electromagnetic driving method, the printing material is replaced with a molten liquid metal substance. Utilizing the magnetohydrodynamic properties of the liquid metal, metal micro-droplets with higher frequencies and droplet masses can be generated and directly used for 3D printing of metal parts, alleviating the technical problems of high raw material costs, expensive equipment, and low printing rates existing in the prior art, resulting in high costs for metal 3D printing.

[0045] On the basis of the above embodiment, further, in a preferred embodiment of the present invention, it further includes a control main body; the control main body is electrically connected to the feeding mechanism 200, the heating mechanism 300, and the electromagnetic driving mechanism 100 respectively. The control main body can adjust the opening and closing of the feeding mechanism 200 to control the height of the liquid surface 500 of the molten metal pool in the crucible 102. By sending the real-time liquid surface height to the control main body, the control main body can control the heating temperature of the heating mechanism 300, and the control main body can control the voltage pulse width modulation waveform applied to both ends of the exciting inductance coil 101 in the electromagnetic driving mechanism 100.

[0046] In this embodiment, the control entity may have a main control chip. Multiple types of control entities can be adopted, such as: MCU, computer, PLC controller, etc. Preferably, the control entity is an MCU, a microcontroller unit (MCU), also known as a single-chip microcomputer or microcontroller. It appropriately reduces the frequency and specifications of the central processing unit and integrates peripheral interfaces such as memory, counter, USB, A / D conversion, UART, PLC, DMA, and even the LCD driver circuit on a single chip, forming a computer at the chip level for different combinations of control in different application scenarios. Preferably, the control entity may be composed of an amplifier circuit, a single-chip microcomputer, a display, etc., which will not be elaborated here.

[0047] As Figure 3 and Figure 4 shown, the crucible 102 and the nozzle 103 are arranged along the vertical direction. When the crucible 102 and the nozzle 103 are heated to a preset temperature, a molten pool is formed inside the crucible 102 and the nozzle 103. The liquid level height of the molten pool is maintained at the liquid level 500 of the metal molten pool. Due to the action of gravity, the internally melted liquid metal has a tendency to extrude downward. At the same time, the liquid metal at the nozzle holes below the nozzle 103 is restricted by the surface tension. The combined action of the two causes the liquid metal to form a meniscus at the nozzle holes below the nozzle 103; the equivalent pressure P g generated by gravity can overcome a part of the surface tension σ.

[0048] As Figure 7 shown, the positive and negative poles of the excitation inductance coil 101 are connected to an external pulse power supply. The pulse power supply generates a pulse voltage with positive and negative alternations. The rise and fall times of the voltage waveform are very short, showing positive and negative polarity alternations on the time axis. Considering the excitation inductance coil 101 as a series connection of an ideal inductor and a pure resistor component, when the voltage waveform is applied to the two poles of the excitation inductance coil 101, under the action of the positive voltage, a charging current is formed inside the excitation inductance coil 101, and the current gradually increases at a certain slope. After the positive pulse voltage returns to zero, the charging ends; under the action of the negative voltage, the current inside the excitation inductance coil 101 decreases at a certain rate. By reasonably controlling the duration of the positive and negative pulses, a triangular wave current as shown in Figure 8 can be formed.

[0049] According to Maxwell's equations, when the pulse power supply provides a positive voltage, the power supply charges the inside of the excitation inductance coil 101. The directions of the magnetic field B inside the coil and the induced current inside the liquid metal are as shown in Figure 3 At this time, the liquid metal will be affected by the Lorentz force, and the direction of the Lorentz force (the direction indicated by the arrow) is as shown in Figure 3As shown, the Lorentz force is applied to the liquid metal in the form of a body force. Under the action of the pulsed Lorentz force, a high-pressure region is formed at the center of the nozzle 103, driving the liquid metal to be extruded in the form of droplets from the lower nozzle holes. Similarly, when a negative voltage is applied across the excitation inductance coil 101, the current inside the excitation inductance coil 101 is rapidly released. At this time, the direction of the magnetic field inside the excitation inductance coil 101, the direction of the induced current inside the liquid metal, and the direction of the Lorentz force are as Figure 4 shown. The liquid metal is subjected to a radially outward acting force, and a low-pressure region is formed at the center of the nozzle 103, driving the liquid metal to contract at the nozzle holes at the bottom of the nozzle 103, pinching off the metal droplets extruded in the previous process. Thus, under the combined action of the positive voltage pulse and the negative voltage pulse, a single metal droplet is extruded from the nozzle 103 and is reliably pinched off, generating molten liquid metal micro-droplets with a vertically downward velocity direction.

[0050] Based on the above process being the generation process of molten liquid metal micro-droplets in a single cycle, during the operation of the device, the frequency and duty cycle of the applied voltage pulse can be changed, thereby controlling the molten liquid metal inside the crucible 102 to be ejected from the nozzle holes at the bottom of the nozzle 103 at different frequencies, obtaining a metal "droplet string" with a very high emission frequency for use in metal additive manufacturing processes.

[0051] In a preferred embodiment of the present invention, it further includes a housing 400 and a thermal insulation layer 411; the heating mechanism 300, the feeding mechanism 200, and the electromagnetic driving mechanism 100 are all installed inside the housing 400. The housing 400 has a sandwich layer, and the thermal insulation layer 411 is filled in the sandwich layer, and the thermal insulation layer 411 is evenly arranged along the circumferential direction of the housing 400.

[0052] In this embodiment, the housing 400 serves as a protective structure for the overall structure. By installing the heating mechanism 300, the feeding mechanism 200, and the electromagnetic driving mechanism 100 inside the housing 400 and using the housing 400 with a thermal insulation layer 411 arranged in a ring shape, it ensures the heating and melting of the metal wire material in the crucible 102 and the nozzle 103 by the heating mechanism 300, and at the same time can also ensure the integrity and sealing requirements of the device.

[0053] In a preferred embodiment of the present invention, the housing 400 includes an outer housing main body 401, an upper end cover 402, an inner housing main body 403, and a nozzle housing 404; the outer housing main body 401 is provided with an accommodation space, the inner housing main body 403 is located inside the accommodation space, and the inner housing main body 403 abuts against the inner wall of the outer housing main body 401. The upper end cover 402 is hermetically connected to the end of the outer housing main body 401, and the upper end cover 402 is connected to the inner housing main body 403. The nozzle housing 404 is sleeved outside the nozzle 103, and the inner housing main body 403 abuts against and is fixed to the nozzle housing 404.

[0054] In this embodiment, during the assembly process of the outer shell main body 401, the upper end cover 402, the inner shell main body 403, and the nozzle outer shell 404 in sequence, good airtightness needs to be maintained. Among them, the outer shell main body 401 can be in a columnar structure. One end of the outer shell main body 401 has an opening, and a nozzle channel is provided at the other end of the outer shell main body 401. The inner shell main body 403 can be accommodated and assembled inside the accommodation space, and the upper end cover 402 can be hermetically assembled with the opening of the outer shell main body 401, and the upper end cover 402 can be assembled and abutted against the inner shell main body 403. Through the inner shell main body 403, the heating mechanism 300 and the crucible 102 can be supported and fixed. And when the nozzle 103 is arranged through the nozzle channel, the nozzle 103 can be protected externally by the nozzle outer shell 404. Among them, the heat insulation layer 411 can be arranged annularly along the outer shell main body 401, and the temperature of the accommodation space can be ensured through the outer shell main body 401 and the heat insulation layer 411.

[0055] In a preferred embodiment of the present invention, the housing 400 further includes a crucible fixing frame 405; the crucible fixing frame 405 is located between the inner shell main body 403 and the crucible 102. The crucible fixing frame 405 clamps the outside of the crucible 102, and the crucible fixing frame 405 and the inner shell main body 403 are fixed by stepped clamping.

[0056] In this embodiment, the crucible fixing frame 405 can adopt an annular support plate. The crucible fixing frame 405 can clamp and fix the outside of the crucible 102, and the crucible fixing frame 405 can be fixed to the inner wall of the inner shell main body 403 by stepped clamping in sequence. By using the crucible fixing frame 405, it can be ensured that the crucible 102 and the nozzle 103 are vertically arranged along the extension of the nozzle channel.

[0057] In a preferred embodiment of the present invention, the feeding mechanism 200 includes a wire material supply pipeline 201, a laser displacement sensor 202, and a quartz window 203; an observation hole is provided on the upper end cover 402. The quartz window 203 is hermetically connected to the observation hole, and a feeding channel is provided on the quartz window 203. The wire material supply pipeline 201 extends into the accommodation space through the feeding channel, and the wire material supply pipeline 201 is communicated with the crucible 102. The wire material supply pipeline 201 is communicated with an external wire material conveying mechanism; the laser displacement sensor 202 is arranged corresponding to the quartz window 203. The laser displacement sensor 202 is electrically connected to the control main body. The laser displacement sensor 202 is used to detect the height information of the metal molten pool liquid level 500 in the crucible 102 and transmit this height information to the control main body, and the control main body correspondingly controls the external wire material conveying mechanism to convey wire material to the wire material supply pipeline 201.

[0058] In this embodiment, the molten liquid metal in the crucible 102 is ejected downward from the nozzle 103 in the form of high-frequency droplets (usually dozens to hundreds of Hz). The liquid level 500 of the metal molten pool gradually decreases as the ejection progresses. The laser displacement sensor 202 emits a laser beam towards the liquid level. The laser beam passes through the quartz window 203 above the liquid level and is reflected on the upper surface of the liquid level 500 of the metal molten pool. The reflected laser beam is received by the laser displacement sensor 202, and the relative distance between the liquid level 500 of the metal molten pool and the laser displacement sensor 202 is converted into the real-time height of the liquid level of the liquid metal in the crucible 102. The control main body collects the analog quantity of the liquid level height output by the laser displacement sensor 202 in real time, and controls the feeder to feed the metal wire material into the crucible 102 from the metal wire material supply channel. The newly fed metal wire material melts above the molten pool and continuously replenishes the metal in the crucible 102, thereby maintaining the dynamic stability of the liquid level 500 of the metal molten pool.

[0059] In a preferred embodiment of the present invention, the heating mechanism 300 includes a heating coil electrode 301, a heating coil 302, a thermocouple connecting pipe 303, and a thermocouple 304. The upper end cover 402 is provided with an electrode hole and a through hole for the thermocouple 304. The heating coil 302 is arranged annularly along the outside of the crucible 102. The heating coil electrode 301 passes through the electrode hole and is electrically connected to the heating coil 302, and the heating coil electrode 301 is hermetically connected to the electrode hole. The thermocouple 304 is attached to the outer side wall of the crucible 102, and the thermocouple connecting pipe 303 passes through the through hole for the thermocouple 304 and is electrically connected to the thermocouple 304. The thermocouple 304 is electrically connected to the control main body. The thermocouple 304 is used to detect the temperature information of the crucible 102 and transmit this temperature information to the control main body, and the control main body correspondingly controls the voltage and output power of the heating coil electrode 301.

[0060] In this embodiment, the heating coil electrode 301 includes two heating coil electrodes 301. The two heating coil electrodes 301 pass through the electrode hole of the upper end cover 402, and their lower parts are respectively connected to both ends of the heating coil 302 inside the inner shell main body 403. The end parts of the two heating coil electrodes 301 extending out of the upper end cover 402 are respectively connected to the positive and negative poles of an external low-voltage temperature control power supply to ensure good contact between the electrodes and minimize the contact resistance between the electrodes to avoid excessive heating at the electrodes. The specific resistance is jointly determined according to the overall heating power of the device and the output voltage of the external low-voltage temperature control power supply.

[0061] Furthermore, the thermocouple connecting tube 303 extends into the interior of the accommodation space through the thermocouple 304 through-hole of the upper end cover 402, and the thermocouple 304 is connected to the control body through the thermocouple connecting tube 303; by presetting the metal material type in the control body and reasonably designing the total resistance of the heating coil 302, the voltage and output power of the external low-voltage temperature control power supply according to the metal material type to be printed, the crucible 102 and the nozzle 103 inside the accommodation space can be heated and maintained at a specified temperature, and it is ensured that the metal material inside the crucible 102 is reliably melted. For example, the heating temperature ranges for different metal materials are: aluminum (800°C - 850°C), copper (1300°C - 1400°C), 316L stainless steel (1300°C - 1400°C).

[0062] Optionally, there can be various types of heating coil electrodes 301, such as: graphite heating coil electrode 301 or ceramic heating coil electrode 301, etc. Preferably, the heating coil electrode 301 can adopt the graphite heating coil electrode 301.

[0063] To ensure the airtightness inside the accommodation space, in a preferred embodiment of the present invention, the thermocouple connecting tube 303 and the thermocouple 304 through-hole are sealed with ceramic glue.

[0064] In a preferred embodiment of the present invention, an inert gas channel 412 is opened on the upper end cover 402, and the inert gas channel 412 communicates with the inside of the crucible 102.

[0065] In this embodiment, during the working process, an inert gas (such as argon) with a slightly positive pressure (greater than 1 atm) enters the interior of the accommodation space from the inert gas channel 412 and is discharged together with the molten metal droplets by wrapping them from the opening below the nozzle housing 404, forming a flowing inert gas atmosphere inside the accommodation space to protect the heating coil 302, the crucible 102, the nozzle 103 and the internal metal molten pool from oxidation in a high-temperature environment.

[0066] In a preferred embodiment of the present invention, the electromagnetic drive mechanism 100 further includes an excitation coil water-cooling ring 104, a water-cooling ring sealing cover 105, and a sealing ring 106; the excitation coil water-cooling ring 104 is located at one end of the housing main body 401 away from the upper end cover 402, the water-cooling ring sealing cover 105 is located between the excitation coil water-cooling ring 104 and the housing main body 401, the water-cooling ring sealing cover 105 is respectively connected to the excitation coil water-cooling ring 104 and the housing main body 401, the sealing ring 106 is located between the excitation coil water-cooling ring 104 and the water-cooling ring sealing cover 105, and the excitation coil water-cooling ring 104 is sleeved outside the nozzle housing 404; the excitation coil water-cooling ring 104 is provided with an annular channel 114, a water inlet 124, and a water outlet 134, the water inlet 124 and the water outlet 134 are respectively located on opposite sides of the annular channel 114, the excitation inductance coil 101 is accommodated in the annular channel 114, and a coolant is used to flow in the annular channel 114 to adjust the temperature of the excitation inductance coil 101.

[0067] In this embodiment, the excitation coil water-cooling ring 104 is annularly arranged outside the nozzle 103, and the excitation inductance coil 101 is located in the annular channel 114. The annular channel 114 can be used as a sealed space to accommodate the excitation inductance coil 101. In order to ensure the temperature range in the annular channel 114, a water inlet 124 and a water outlet 134 are provided on opposite sides of the annular channel 114. The coolant is conveyed into the annular channel 114 through the water inlet 124, and after the coolant exchanges heat with the excitation inductance coil 101, it is discharged through the water outlet 134, ensuring the overall temperature range of the excitation inductance coil 101 and the excitation coil water-cooling ring 104; further, the excitation coil water-cooling ring 104 is in sealing connection with the housing main body 401 through the water-cooling ring sealing cover 105, and the excitation coil water-cooling ring 104 and the water-cooling ring sealing cover 105 are sealed through the sealing ring 106. Preferably, the sealing ring 106 can be an O-ring.

[0068] The metal micro-droplet additive manufacturing device provided in this embodiment can be combined with 3D metal printing control software. The metal micro-droplet additive manufacturing device is installed on a guide rail slider that can move up and down in the vertical direction, and a two-dimensional displacement platform is arranged below the metal micro-droplet additive manufacturing device to move arbitrarily in two mutually perpendicular directions, thus constituting the displacement mechanism for 3D printing. The printing substrate can adopt a high-temperature ceramic heating plate, and the corresponding substrate temperature is set according to the printed metal material during the printing process. Generally, the temperature of the printing substrate needs to be slightly lower than the melting point of the metal material. The three-dimensional part is sliced layer by layer using slicing software, and a path file in the format of G-code (G-code) is given. The upper computer controls the three-dimensional displacement slider to generate corresponding displacements according to the path planned by the G-code. During the printing process, due to the complex geometric structure of the part, the metal micro-droplet additive manufacturing device needs to be repeatedly turned on and off during the process of layer-by-layer spraying and depositing liquid metal micro-droplets. Therefore, reasonable voltage and current parameters need to be generated by an external pulse power supply so that the spraying state (shape, size) of the high-frequency metal droplets can remain stable during the on and off processes. The on and off control signals of the metal micro-droplet additive manufacturing device are both sent by the control main body. The control main body can control the output voltage waveform of the pulse power supply by generating a set of symmetric PWM (Pulse Width Modulation) waveforms and controlling the conduction of IGBT (Insulated Gate Bipolar Transistor) devices.

[0069] Specifically, the control main body monitors in real time whether metal droplet filling is required in the current printing path. If metal droplet filling is required, a dual-channel symmetric PWM wave signal is sent to the pulse power supply. The pulse power supply outputs positive and negative alternating pulses to repeatedly charge and discharge the excitation inductance coil 101. If metal droplet filling is not required in the current printing path, the PWM wave output is stopped, the pulse power supply also stops outputting pulse voltage, and there is no charging and discharging current inside the excitation inductance coil 101, so the droplet spraying stops. As Figure 9 shown, the control main body generates two PWM waves and simultaneously loads them on the IGBTs (Q1~Q4) in the H-bridge circuit (electronic circuit). When Q1 and Q4 are in the high-level section, Q2 and Q3 are in the low-level section, Q1 and Q4 are conducting, and Q2 and Q3 are cut off. The power supply VCC charges the excitation inductance coil 101 along the arrow direction, and a charging current is formed inside the excitation inductance coil 101, corresponding to Figure 8 the rising edge of the triangular wave (approximate); as Figure 10 shown, when Q1 and Q4 are in the low-level section, Q2 and Q3 are in the high-level section, Q1 and Q4 are cut off, and Q2 and Q3 are conducting. The voltage applied across the excitation inductance coil 101 is reversed, and the current inside the coil is quickly released. This process corresponds to Figure 8The falling edge of the triangular wave (approximate); when all four IGBTs (Q1 to Q4) are turned off, there is no voltage input on both sides of the excitation inductance coil 101, and at this time, the electromagnetic drive metal droplet ejection process stops.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A metal droplet additive manufacturing device, characterized in that, Including: a heating mechanism (300), a feeding mechanism (200), and an electromagnetic driving mechanism (100); The electromagnetic driving mechanism (100) includes an exciting inductance coil (101), a crucible (102), and a nozzle (103); the feeding mechanism (200) is internally connected to the crucible (102), the feeding mechanism (200) is used to convey metal wire materials into the crucible (102), the heating mechanism (300) is annularly arranged outside the crucible (102), and the heating mechanism (300) is used to heat and melt the metal wire materials in the crucible (102) to form a liquid metal pool; The nozzle (103) is connected to the crucible (102), the exciting inductance coil (101) is annularly arranged outside the nozzle (103), and the exciting inductance coil (101) is used to provide a Lorentz force into the nozzle (103) under the action of energization to control the liquid metal in the nozzle (103) to form metal micro-droplets for spraying or droplet pinching-off to stop; It further includes a control body; The control body is electrically connected to the feeding mechanism (200), the heating mechanism (300), and the electromagnetic driving mechanism (100) through electrical signals respectively; It further includes a housing (400), and the housing (400) includes an outer housing body (401), an upper end cover (402), an inner housing body (403), and a nozzle housing (404); The outer housing body (401) is provided with an accommodating space, the inner housing body (403) is located in the accommodating space, and the inner housing body (403) abuts against the inner wall of the outer housing body (401), the upper end cover (402) is hermetically connected to the end of the outer housing body (401), and the upper end cover (402) is connected to the inner housing body (403), the nozzle housing (404) is sleeved outside the nozzle (103), and the inner housing body (403) is fixedly abutted against the nozzle housing (404); The feeding mechanism (200) includes a metal wire material supply pipeline (201), a laser displacement sensor (202), and a quartz window (203); An observation hole is opened on the upper end cover (402), the quartz window (203) is hermetically connected to the observation hole, and a feeding channel is opened on the quartz window (203), the metal wire material supply pipeline (201) extends into the interior of the accommodating space through the feeding channel, and the metal wire material supply pipeline (201) is connected to the crucible (102), and the metal wire material supply pipeline (201) is connected to an external metal wire material conveying mechanism; The laser displacement sensor (202) is correspondingly arranged with the quartz window (203), the laser displacement sensor (202) is electrically connected to the control body, the laser displacement sensor (202) is used to detect the height information of the liquid metal surface (500) in the crucible (102) and convey this height information to the control body, and the control body correspondingly controls the external metal wire material conveying mechanism to convey metal wire materials to the metal wire material supply pipeline (201); The electromagnetic drive mechanism (100) further includes an excitation coil water cooling ring (104), a water cooling ring sealing cover (105), and a sealing ring (106). The excitation coil water cooling ring (104) is located at one end of the housing main body (401) away from the upper end cover (402). The water cooling ring sealing cover (105) is located between the excitation coil water cooling ring (104) and the housing main body (401). The water cooling ring sealing cover (105) is connected to the excitation coil water cooling ring (104) and the housing main body (401) respectively. The sealing ring (106) is located between the excitation coil water cooling ring (104) and the water cooling ring sealing cover (105). The excitation coil water cooling ring (104) is sleeved outside the nozzle housing (404).

2. The metal droplet additive manufacturing device according to claim 1, characterized in that, The control body can control the heating temperature of the heating mechanism (300), and the control body can control the voltage pulse width modulation waveform applied across the excitation inductance coil (101) in the electromagnetic drive mechanism (100).

3. The metal droplet additive manufacturing device according to claim 1, characterized in that, It further includes a heat preservation layer (411). The heating mechanism (300), the feeding mechanism (200), and the electromagnetic drive mechanism (100) are all installed inside the housing (400). The housing (400) has a sandwich layer, and the heat preservation layer (411) is filled in the sandwich layer. The heat preservation layer (411) is evenly arranged along the circumferential direction of the housing (400).

4. The metal droplet additive manufacturing device according to claim 1, wherein, The housing (400) further includes a crucible fixing frame (405). The crucible fixing frame (405) is located between the inner housing main body (403) and the crucible (102). The crucible fixing frame (405) clamps the outside of the crucible (102), and the crucible fixing frame (405) is fixed to the inner housing main body (403) by step clamping.

5. The metal micro-droplet additive manufacturing device according to claim 1, characterized in that, The heating mechanism (300) includes a heating coil electrode (301), a heating coil (302), a thermocouple connecting pipe (303), and a thermocouple (304). An electrode hole and a through hole for the thermocouple (304) are formed on the upper end cover (402). The heating coil (302) is arranged in a ring along the outside of the crucible (102). The heating coil electrode (301) penetrates through the electrode hole and is electrically connected to the heating coil (302), and the heating coil electrode (301) is hermetically connected to the electrode hole. The thermocouple (304) is attached to the outer side wall of the crucible (102). The thermocouple connecting pipe (303) penetrates through the through hole for the thermocouple (304) and is electrically connected to the thermocouple (304). The thermocouple (304) is electrically connected to the control body. The thermocouple (304) is used to detect the temperature information of the crucible (102) and transmit this temperature information to the control body, and the control body correspondingly controls the voltage and output power of the heating coil electrode (301).

6. The metal droplet additive manufacturing device according to claim 5, wherein The thermocouple connecting pipe (303) is sealed with the through hole for the thermocouple (304) by ceramic glue.

7. The metal droplet additive manufacturing device according to any one of claims 4-6, characterized in that The water-cooling ring (104) of the exciting coil is provided with an annular channel (114), a water inlet (124) and a water outlet (134). The water inlet (124) and the water outlet (134) are respectively located on opposite sides of the annular channel (114). The exciting inductance coil (101) is accommodated in the annular channel (114). A coolant is used to flow in the annular channel (114) to adjust the temperature of the exciting inductance coil (101).

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